1. Field of the Invention
This invention relates to a thermally moldable preform useful for creating custom, quadrant, dental impression trays and to a method of forming trays using the preform.
2. Prior Art
As is a preliminary step to the formation of a denture, a trough-shaped impression tray is filled with a casting material and brought into contact with the section of the dental arch of which the impression is to be made. In the process of forming a sectional impression a quadrant impression tray is employed that fits over half the dental arch and has a projecting handle at its forward end. These quadrant trays are available in either a first form that may be used with either the maxillary left quadrant or the mandibular right quadrant, or a second form that may be used with either the maxillary right quadrant or the mandibular left quadrant. The appropriate tray is filled with impression material and brought into contact with a section of the dental arch to form an impression. The resultant casting is used to form a custom impression tray which closely follows the contours of the dental arch and teeth so that when it is filled with impression material a final impression may be taken having relatively constant wall thickness to equalize the pressure on all points.
Typically, the time and expertise required to form a final impression tray from the initial impression necessitates two vists or considerable waiting from the patient to the dentist; one to form the initial impression and a second to form the final impression using the final tray.
Copending patent application Ser. No. 843,433 entitled "Anatomical Intra-Orally Moldable Dental Impression Tray and Method of Using the Same" discloses a thermally moldable impression tray that may be used by a dentist to form a final impression in a single session, eliminating the delay and cost of the two-step process. The impression tray of that application is formed of a thermo-plastic having a glass transition temperature slightly above body temperature and below a temperature that would cause discomfort to the patient's mouth. The impression tray is heated above its softening temperature externally of the mouth and is then placed within the mouth and shaped to conform to the patient's oral tissue. The tray is then allowed to cool below its glass transition temperature while in the mouth. When removed and chilled to room temperature, the resultant tray has all the attributes of a custom impression tray and may be immediately used to form a final impression. The previous application discloses full impression trays of a first type for use within the mandibular section and of a second type for use with a maxillary section.
The present invention constitutes an application of the principles of that previous invention to quadrant impression trays in a novel manner that eliminates the need for provision of different forms of quadrant trays for use with different dental sections.